a) Field of the Invention
The invention relates to a barrel pump with a pump rotor which is driven by a motor via a rotor shaft and which is used to pump the liquid upward, in a ring channel of a tubular pump housing, through an inlet opening situated at the bottom end thereof, to an outlet arranged at the top end of the ring channel, the inlet opening being closable by means of a closure body which can be actuated by a relative displacement between rotor shaft and pump housing, and the closure body being designed as a cone seal and, in the open position, being arranged at the bottom end of the pump housing in front of the central inlet opening.
b) Description of the Related Art
A barrel pump of this type is known from DE-A-196 30 347. In this known barrel pump, although the cone seal is situated in front of the inlet opening, it is still inside the pump housing, which is necessary in order for the cone seal to be pressed against the edge of the inlet opening by means of a spring. The cone seal is transferred into the open position by displacement of the rotor shaft, and in the open state the rotor shaft presses continuously against the cone seal, resulting in a relative movement between cone seal and rotor shaft. At the extremely high rotational speeds of the rotor shaft, this leads to rapid wear to the cone seal unless special measures for supporting the rotor shaft are provided in the support region, and such measures increase the structural outlay still further, in addition to the pressure spring which is required. Since the cone seal together with the pressure spring which is required to execute the closure movement has to be arranged inside the pump housing, there is a relatively great distance between the pump rotor and the bottom end of the pump housing.
The primary object of the invention is to design a barrel pump of the generic type in such a way that, while achieving a good level of efficiency in terms of emptying the residues, it requires a lower structural outlay and, in addition, is suitable for all materials used in the pump construction sector.
In a barrel pump of the type explained in the introduction, this object is achieved, according to the invention, by the fact that the cone seal is arranged at the end of the rotor shaft, in such a manner that it can rotate freely thereon and in a form-fitting manner, with a slight axial play, in the axial direction, and can be pulled into the closed position by the relative displacement between rotor shaft and pump housing, and that the cone seal is of elastic design and has a circumferential groove which, in the closed position, can be latched to the edge of the inlet opening.
Since, in this embodiment, only the cone seal has to be designed as an elastic part, and therefore has to consist of a different material from the other parts of the pump, when selecting said material it should be ensured that it is able to withstand the media which are to be conveyed. There are plastics materials, for example ETFE, which are able to withstand most liquids which can be conveyed by pumps which have been introduced onto the market to date. Since, given a suitable selection of materials, the cone seal can be used for all pumps made from different materials, the need to change the design in the event of material changes, which has been established in the known pump, no longer occurs. It is therefore possible with this design according to the invention, starting from a standard barrel pump, by using a longer rotor shaft which projects out of the inlet and by providing a cone seal which is designed in accordance with the invention, if appropriate in combination with a pump base which can be replaced and is usually screwed on, to convert this standard barrel pump into a so-called residue-emptying pump, in which virtually the entire content of a barrel is emptied and it is possible to prevent medium which is to be conveyed and is situated in the pump from running back into the barrel. The requirements which are to be imposed on the pump base are that this base should have an opening edge which is able to form a snap-action closure with the cone seal and, moreover, must ensure protection for the cone seal which is situated in front of the inlet opening. The pump according to the invention has the advantage that the pump rotor can be arranged very closely behind the inlet opening, since the cone seal or the closure body is situated outside the inlet opening, specifically in a space which must in any case be provided in order for the liquid situated in the barrel to be sucked up. Therefore, by arranging the cone seal in front of the inlet opening, the distance between the pump rotor and the inlet opening is reduced to a minimum without the sealing body requiring the distance from the bottom of the barrel to the pump rotor to be increased, since a certain distance between the bottom of the barrel and the inlet opening has to be present in order to ensure that the liquid flows into the inlet. This distance is sufficient to allow the cone seal to be arranged in front of the inlet opening. Due to the elasticity of the cone seal, it latches to the opening edge of the inlet in the manner of a snap-action closure. There is no need for any restoring springs for actuating the closure body, which is designed as a cone seal, and this fact simplifies the structure of the pump. Since the closure body arranged on the rotor shaft is moved into its closed position and its open position by relative displacement between the rotor shaft and the pump housing, additional components for actuating this closure body are not required. This makes the pump of extremely simple structure.
Working on the basis of a barrel pump having a connection head which has the upper rolling-contact bearings, which are designed as fixed bearings, for the rotor shaft and a coupling for a drive motor and which can be connected to the tubular pump housing by means of a screw connection, in a further advantageous configuration of the invention an adjustment ring, which serves as an adjustable stop for the connection head, is screwed onto the external screw thread of the tubular pump housing or of an extension. In this way, it is possible, in a simple manner, to compensate for dimensional changes caused by thermal expansion, so that reliable operation is always possible.
The extension preferably comprises a rotary cap and a groove flange, which together form an adjustment device for displacement of the rotor shaft.
The invention is explained in more detail below with reference to an exemplary embodiment which is illustrated in the drawings.